title: Enhanced thermic effect of food after Roux-en-Y gastric bypass surgery.
abstract: BACKGROUND
  The mechanisms of weight loss after Roux-en-Y gastric bypass (RYGB) surgery are incompletely understood.
  
  
  OBJECTIVE
  Our objective was to investigate changes in metabolic processing of ingested food that may contribute to the weight-reducing effect of RYGB surgery.
  
  
  METHODS
  This was a cross-sectional case-control study at the Interdisciplinary Obesity Center, Cantonal Hospital St. Gallen, St. Gallen, Switzerland.
  
  
  METHODS
  Ten formerly obese women (mean ± SEM body mass index [BMI] = 26.6 ± 0.9 kg/m(2)) who had undergone RYGB surgery 41.9 ± 9.7 months before, 8 severely obese women (BMI = 40.8 ± 2.0 kg/m(2)), and 10 lean women (BMI = 20.9 ± 0.6 kg/m(2)).
  
  
  METHODS
  Intervention was a standardized liquid meal test.
  
  
  RESULTS
  The thermic effect of food (TEF), respiratory quotient, and circulating levels of glucose, insulin, and C-peptide were assessed before and repeatedly during the first 90 minutes after the ingestion of a standardized liquid mixed meal containing 39.2 g carbohydrates, 15.4 g protein, and 2.8 g fat.
  
  
  RESULTS
  TEF area under curve (0-90 minutes) was significantly greater in RYGB patients than in severely obese and lean women (both P < .01). After ingestion of the mixed meal, the respiratory quotient increased to significantly greater values in the RYGB patients than in the severely obese and lean group (P < .001 for ANOVA time × group interaction). Also, the postprandial rise in circulating glucose, insulin, and C-peptide levels was remarkably higher in the RYGB patients than in the other 2 groups (all P < .001 for ANOVA time × group interaction).
  
  
  CONCLUSIONS
  Data demonstrate an enhanced TEF after RYGB surgery. Although this observation likely contributes to the weight-reducing effects of the surgery, data also point to an altered metabolic processing of food in RYGB patients characterized by an enhanced glucose absorption and postprandial carbohydrate oxidation.
authors.affiliation: Obesity Center, Cantonal Hospital 9016 St. Gallen, 9016 St. Gallen, Switzerland.
authors.forename: Britta
authors.initials: B
authors.lastname: Wilms
authors.forename: Barbara
authors.initials: B
authors.lastname: Ernst
authors.forename: Sebastian M
authors.initials: SM
authors.lastname: Schmid
authors.forename: Martin
authors.initials: M
authors.lastname: Thurnheer
authors.forename: Bernd
authors.initials: B
authors.lastname: Schultes
mesh_terms: D000328:Adult; D001786:Blood Glucose / Q000378:metabolism; D001794:Blood Pressure / Q000502:physiology; D002096:C-Peptide / Q000097:blood; D002153:Calorimetry, Indirect; D016022:Case-Control Studies; D003430:Cross-Sectional Studies; D004734:Energy Metabolism / Q000502:physiology*; D005260:Female; D005502:Food; D015390:Gastric Bypass; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D007328:Insulin / Q000097:blood; D008875:Middle Aged; D009765:Obesity / Q000378:metabolism / Q000503:physiopathology* / Q000601:surgery; D019518:Postprandial Period; D022722:Thermogenesis / Q000502:physiology*
chemical_list: D001786:Blood Glucose; D002096:C-Peptide; D007328:Insulin